drm/sun4i: vi_layer: use layer struct instead of multiple args

drm/sun4i: vi_layer: use layer struct instead of multiple args

This change is equally a cleanup (less arguments) and preparation for
DE33 separate plane driver. It will introduce additional register space.

No functional changes.

Reviewed-by: Chen-Yu Tsai <wens@kernel.org>
Tested-by: Ryan Walklin <ryan@testtoast.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://patch.msgid.link/20251104180942.61538-18-jernej.skrabec@gmail.com
Signed-off-by: Chen-Yu Tsai <wens@kernel.org>